I'm not going to argue for complex mechanics, because I'm pretty casual and not in the raiding scene. I'm sure plenty of other people more qualified have already shared their piece. What I'll speak about is based on my experience playing and liking RDM in Stormblood and my feeling on it after playing at endgame enough to get i450 gear:

A theme I've felt with jobs the Devs have worked on Shadowbringers is removing abilities and then rewarding them back to us with a new coat of paint. As a WHM main, that's what our capstone ability Temperance feels like: a slightly more powerful Largesse... which is a role-action that was removed. But they gave it back to us as a capstone. Aren't they nice? >_>

RDM feels like was one of the least touched job in that respect. It mostly feels the same, but it's accrued very little over the expansion. Scorch is really the only new thing I really notice. The rest? Trait improvements for the most part. The look and feel is mostly the same.

Except for one thing that irks me enormously: the Red Mage's new AoE spells VerAero 2 and VerThunder 2, followed by either Scatter or Impact. Gone is Scatter+Scatter. Now it's VerAero 2+Impact or VerThunder 2+Impact.

...And it annoys me to no end. I get how they tried to implement something similar to the single-target process... but I appreciated how simple (how braindead) spamming Scatter+Scatter was.

I would have loved Scatter+Scatter to become Scatter+Impact (Scatter was augmented on second cast, so, that would have been cool).